Electrochemical double layer capacitor having carbon powder electrodes

ABSTRACT

A method of making an electrode structure, the electrode structure and a double layer capacitor including the electrode structure, the method comprising the steps of: forming a plurality of electrodes, each having a current collector plate, a primary coating formed on each side of the collector plate, the primary coating including conducting carbon powder and a binder, and a secondary coating formed on each primary coating, the secondary coating including activated carbon powder, a solvent and a binder; positioning a respective separator between each electrodes while stacking the electrodes such that the respective separator is juxtaposed against respective secondary coatings of adjacent electrodes that electrically insulates the adjacent electrodes, whereby forming an electrode stack; and rolling the electrode stack into a cylindrical electrode structure.

This application is related to U.S. Utility patent application Ser. No.10/005,885, filed Nov. 2, 2001 now U.S. Pat. No. 6,643,119, from whichpriority is claimed, and which is hereby incorporated by reference inits entirety, including all tables, figures, and claims.

BACKGROUND OF THE INVENTION

The present invention relates generally to electrochemical double layercapacitors, and more particularly to a high performance electrochemicaldouble layer capacitor made with low-resistance carbon powderelectrodes.

Double layer capacitors, also referred to as electrochemical doublelayer capacitors (EDLC), are energy storage devices that are able tostore more energy per unit weight and unit volume than traditionalcapacitors. In addition, because of their relatively low internalresistance, double layer capacitors can typically be charged and can, inturn, deliver stored energy at a high power rating than rechargeablebatteries.

Double layer capacitors may consist of two carbon electrodes that areisolated from electrical contact by a porous separator. Both the porousseparator and the electrodes are immersed in an electrolyte solution,allowing ionic current (ionic flow) to flow between the electrodesthrough the separator at the same time that the separator prevents anelectrical or electronic (as opposed ton an ionic) current from shortingthe two carbon electrodes.

Coupled to the back of each of the two carbon electrodes is typically acurrent collecting plate. One purpose of the current collecting platesis to reduce ohmic losses, i.e., internal resistant, in the double layercapacitor.

Double layer capacitors store electrostatic energy in a polarized liquidlayer that forms when an electrical potential exists between the twocarbon electrodes immersed in an electrolyte (or electrolyte solution).When the electrical potential is applied across the electrodes, a doublelayer of positive and negative charges is formed at theelectrode-electrolyte interface (hence, the name “double layer”capacitor) by the polarization of electrolyte ions due to chargeseparation under the applied electrical potential, and also due todipole orientation and alignment of electrolyte molecules over an entiresurface of the electrodes.

Fabrication of double layer capacitors with carbon electrodes isdescribed in U.S. Pat. Nos. 2,800,616 (Becker), and 3,648,126 (Boos etal.).

A major problem in many carbon-electrode capacitors, includingelectrochemical double layer capacitors with carbon electrodes, is thatthe performance of the carbon-electrode capacitor is often limitedbecause of high internal resistance related to the carbon electrodes.This high internal resistance may be due to several factors, includinghigh contact resistance of carbon-carbon contacts within the carbonelectrodes, and further including high contact resistance of theelectrode-current collector contacts. This high internal resistancetranslates to large ohmic losses in the carbon-electrode capacitorduring charging and discharging of the carbon-electrode capacitor. Thesehigh ohmic losses further adversely affect, i.e., increase, acharacteristic RC (resistance times capacitance) time constant of thecapacitor and thus interfere with the carbon-electrode capacitor'sability to be efficiently charged and/or discharged in a short period oftime.

There is thus a need in the art for systems and methods that lower theinternal resistance within a carbon-electrode capacitor, and hence lowerthe characteristic RC time constant, of the carbon-electrode capacitors,as well as other improvements.

U.S. Pat. No. 5,907,472 to Farahmandi et al., the complete disclosure ofwhich is incorporated herein by reference, discloses a multi-electrodedouble layer capacitor having aluminum-impregnated carbon clothelectrodes. The use of the aluminum-impregnated carbon cloth electrodesdescribed therein results in an electrochemical double layer capacitorhaving a very low internal resistance.

U.S. patent application Ser. No. 09/569,679 of Nanjundiah et al., thecomplete disclosure of which is incorporated herein by reference,discloses an electrochemical double layer capacitor havinglow-resistance carbon powder electrodes.

There is also a continuing need for improved electrochemical doublelayer capacitors. Such improved electrochemical double layer capacitorsneed to deliver large amounts of useful energy at a very high poweroutput, and very high energy density ratings within a relatively shortperiod of time. Such improved electrochemical double layer capacitorsshould also have a relatively low internal resistance, and hence arelatively low characteristic RC time constant, and yet be capable ofyielding a relatively high operating voltage.

Furthermore, it is apparent that improvements are needed in thetechniques and methods of fabricating electrochemical double layercapacitor electrodes so as to lower the internal resistance of theelectrochemical double layer capacitor, and hence lower thecharacteristic RC time constant and maximize the operating voltage.

Since capacitor energy density increases with the square of theoperating voltage, higher operating voltages thus translate directlyinto significantly higher energy densities and, as a result, higherpower output ratings. Thus, improved techniques and methods are neededto lower the internal resistance of the electrodes used within anelectrochemical double layer capacitor and increase the operatingvoltage.

SUMMARY OF THE INVENTION

The present invention advantageously addresses the needs above as wellas other needs by providing a method of making an electrode structurefor use in an electrochemical double layer capacitor.

In one embodiment, the invention may be characterized as a method ofmaking an electrode structure for use in a double layer capacitor,comprising the steps of: forming a plurality of electrodes, each of theplurality of electrodes comprising: a current collector plate; a primarycoating formed on a portion of each side of the current collector plate,the primary coating including conducting carbon powder and a binder; anda secondary coating formed on each primary coating, the secondarycoating including activated carbon powder, a solvent and a binder;positioning a respective separator between each of the plurality ofelectrodes while stacking the plurality of electrodes on top of eachother such that the respective separator is juxtaposed againstrespective secondary coatings of adjacent ones of the plurality ofelectrodes, wherein the respective separator electrically insulates theadjacent ones of the plurality of electrodes from each other, wherebyforming a stack of the plurality of electrodes with a respectiveseparator positioned in between respective ones of the plurality ofelectrodes; and rolling the electrode stack starting at one end of theelectrode stack into a cylindrical structure.

In another embodiment, the invention may be characterized as a method ofmaking an electrode structure for use in a double layer capacitor,comprising the steps of: forming a plurality of electrodes, each of theplurality of electrodes comprising: a current collector plate having alength and a width and a thickness; a primary coating formed on aportion of each side of the current collector plate, the portioncovering an area extending the full length of the current collectorplate and extending a portion of the width of the current collectorplate, the primary coating including conducting carbon powder and abinder; and a secondary coating formed on each primary coating, thesecondary coating including activated carbon powder, a solvent and abinder; positioning a respective separator between each of the pluralityof electrodes while stacking the plurality of electrodes on top of eachother such that the respective separator is juxtaposed againstrespective secondary coatings of adjacent ones of the plurality ofelectrodes, wherein the respective separator electrically insulates theadjacent ones of the plurality of electrodes from each other, wherebyforming a stack of the plurality of electrodes with a respectiveseparator positioned in between respective ones of the plurality ofelectrodes, the electrode stack having-a stack length and a stack width;and rolling the electrode stack starting at one end of the electrodestack along the stack length into a cylindrical structure.

In yet another embodiment, the invention may be characterized as anelectrode structure for use in a double layer capacitor comprising: arolled electrode stack comprising: a plurality of electrodes, each ofthe plurality of electrodes comprising: a current collector foil; aprimary coating formed on a portion of each side of the currentcollector foil, the primary coating including conducting carbon powderand a binder; and a secondary coating formed on each primary coating,the secondary coating including activated carbon powder, a solvent and abinder. The rolled electrode stack also comprises a respective separatorpositioned between each of the plurality of electrodes in a stack suchthat the respective separator is juxtaposed against respective secondarycoatings of adjacent ones of the plurality of electrodes. The respectiveseparator electrically insulates the adjacent ones of the plurality ofelectrodes from each other. The electrode stack is rolled starting atone end of the electrode stack into a cylindrical structure to form therolled electrode stack.

In a further embodiment, the invention may be characterized as a doublelayer capacitor comprising a capacitor can having a first terminal and asecond terminal and a rolled electrode structure contained within thecapacitor can. The rolled electrode structure comprising a plurality ofelectrodes, each of the plurality of electrodes comprising a currentcollector foil and a primary coating formed on a portion of each side ofthe current collector foil. The primary coating includes conductingcarbon powder and a binder. Each electrode also includes a secondarycoating formed on each primary coating. The secondary coating includesactivated carbon powder, a solvent and a binder. Also, a respectiveseparator is positioned between each of the plurality of electrodes in astack such that the respective separator is juxtaposed againstrespective secondary coatings of adjacent ones of the plurality ofelectrodes. The respective separator electrically insulates the adjacentones of the plurality of electrodes from each other. The electrode stackis rolled starting at one end of the electrode stack into a cylindricalstructure to form the rolled electrode structure. And, the capacitorincludes an electrolytic solution contained within the capacitor can.

A better understanding of the features and advantages of the presentinvention will be obtained by reference to the following detaileddescription of the invention and accompanying drawings which set forthan illustrative embodiment in which the principles of the invention areutilized.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will be more apparent from the following more particulardescription thereof presented in conjunction with the following drawingswherein;

FIG. 1 is cross-sectional view of a carbon electrode including a foilcollector, a first layer of conducting carbon, and a second layer ofactivated carbon, in accordance with one embodiment of the presentinvention;

FIG. 2 is a schematic diagram illustrating slurry transfer apparatus andprocess for applying carbon powder slurry, such as conducting carbonpowder slurry or activated carbon powder slurry, to a surface of a foil,so as to form the first layer of conducting carbon or the second layerof activated carbon on the surface of the foil, so as to form the foilelectrode of FIG. 1;

FIG. 3 is a top view of the foil, the carbon powder slurry, and a row awipers that remove the carbon powder slurry-from three strips (or lanes)of the foil as the foil passes through the slurry transfer apparatus ofFIG. 2., so as to form contact edges of the foil electrode of FIG. 1;

FIG. 4 is a top view of a foil having three lanes of the foil (with thecarbon powder slurry having been removed by the wipers of FIG. 3)separated by regions coated with a first layer of conducting carbon anda second layer of activated carbon;

FIG. 5 is a side cross-sectional view of the foil of FIG. 4 having threelanes of the foil separated by regions coated with the first layer ofconducting carbon and a second layer of activated carbon;

FIG. 6 is a top view of the foil of FIG. 4 having been cut into two foilelectrodes, such as the foil electrode in FIG. 1;

FIG. 7 is a side cross-sectional view of two foil electrodes havingtheir respective second layers of activated carbon juxtaposed against aporous separator, so as to form first and second carbon electrodeselectrically (but not ionically) isolated from one another by the porousseparator;

FIG. 8 is a side cross-sectional view of the foil of FIG. 4 wherein bothfirst and second sides of the foil include regions having the firstlayer of conducting carbon and the second layer of activated carbon, andfurther include three lanes of the foil separated by the regions coatedwith the first layer of conducting carbon and a second layer ofactivated carbon;

FIG. 9 is a side cross-sectional view of three foil electrodes, such asin FIG. 8, having first and second sides including the first layer ofconducting carbon and the second layer of activated carbon, with onesecond layer of activated carbon of first and second ones of the foilelectrodes juxtaposed against respective sides of a first porousseparator, and another second layer of activated carbon of second andthird ones of the foil electrodes juxtaposed against respective sides ofa second porous separator, so as to form first, second and third carbonelectrodes electrically (but not ionically) isolated from one another bythe first and second porous separators;

FIG. 10 is a partial top view illustrating windings comprising a pair ofthe carbon electrodes, such as in FIG. 8, having first and second sidesincluding the first layer of conducting carbon and the second layer ofactivated carbon, and being separated by a porous separator;

FIG. 11 is an end assembly cross-sectional view of a “jellyroll”electrode assembly comprising a pair of the carbon electrodes, such asin FIG. 8, having first and second sides including the first layer ofconducting carbon and the second layer of activated carbon, and beingseparated by a first and second porous separator in accordance with a“jellyroll” embodiment employing the winding layers of FIG. 10;

FIG. 12 is a perspective view of the “jellyroll” electrode assembly ofFIG. 10 including with aluminum arc sprayed regions at an end of the“jellyroll” electrode assembly so as to provide a low resistance pathbetween contact edges of the first carbon electrode, and includingadditional arc sprayed regions at an opposite end of the “jellyroll”electrode assembly so as to provide another low resistance path betweencontact edges of the second carbon electrode;

FIG. 13 is a side cross-sectional view of the “jellyroll” electrodeassembly of FIG. 11, having the winding layers of FIG. 10;

FIG. 14 is a side cross-sectional view of the “jellyroll” electrodeassembly of FIG. 11, having the winding layers of FIG. 10, and furtherhaving a first plug;

FIG. 15 is a side cross-sectional view of the “jellyroll” electrodeassembly of FIG. 11, having the winding layers of FIG. 10, and the firstplug of FIG. 14, and further having a remainder of a first terminalassembly;

FIG. 16 is a side cross-sectional view of the “jellyroll” electrodeassembly of FIG. 11, having the winding layers of FIG. 10, the firstplug of FIG. 14 and the remainder of a first terminal assembly of FIG.15, and further having a second plug, a second collector disk and asecond terminal post;

FIG. 17 is a side, exploded cross-sectional view of the “jellyroll”electrode assembly of FIG. 11, having the winding layers of FIG. 10, thefirst plug of FIG. 14, the remainder of the first terminal assembly ofFIG. 15 and the second plug, the second collector disk and the secondterminal post of FIG. 16, and further having a first insulating washer,and a can;

FIG. 18 is a partial side cross-sectional view of the “jellyroll”electrode assembly of FIG. 11, having the winding layers of FIG. 10, thefirst plug of FIG. 14, the remainder of the first terminal assembly ofFIG. 15, the second plug, the second collector disk and the secondterminal post of FIG. 16, and the first insulating washer, and the canFIG. 17, and further having a second insulating washer, a flat washer, aBelleville washer and a locknut;

FIG. 19 a partial side cross-sectional view of the “jellyroll” electrodeassembly of FIG. 12, having the winding layers of FIG. 11, the firstplug of FIG. 14, the remainder of the first terminal assembly of FIG.15, the second plug, the second collector disk and the second terminalpost of FIG. 16, the first insulating washer, and the can FIG. 17, thesecond insulating washer, the flat washer, the Belleville washer and thelocknut of FIG. 18;

FIG. 20 is a perspective view of an electrochemical double layercapacitor made in accordance with the “jellyroll” embodiment of FIG. 19;

FIG. 21 is a side cross-sectional view of a variation of the “jellyroll”embodiment of FIGS. 12 through 20, having an improved collector plate,and a reduced number of parts in a first terminal assembly, and a secondterminal assembly;

FIG. 22 is a top view of a stud/collector disk/terminal post of thesecond terminal of the variation of FIG. 21;

FIG. 23 is a side view of a stud/collector disk/terminal post such as inFIG. 22 of the second terminal of the variation of FIG. 21;

FIG. 24 is a side view of a stud/collector disk of the first terminal ofthe variation of FIG. 21;

FIG. 25 is a top view of a stud/collector disk of the first terminal ofthe variation of FIG. 21;

FIG. 26 is a side cross-sectional view of another variation of the“jellyroll” embodiment of FIGS. 12 through 20, employing a pocket in thecan in a modified second electrode assembly;

FIG. 27 is a side cross-sectional view of another variation of the“jellyroll” embodiment of FIGS. 12 through 20, employing a crimp seal tosecure a lid to the can, and employing a pocket in the lid in a modifiedfirst electrode assembly;

FIG. 28 is a side cross-sectional view of another variation of the“jellyroll” embodiment of FIGS. 12 through 20, employing a low profile“can-within-a-can” assembly and modified first and second electrodeassemblies; and

FIG. 29 is a side cross-sectional view of another variation of the“jellyroll” embodiment of FIGS. 12 through 20, employing a ceramic sealbetween the lid and the first terminal assembly.

Corresponding reference characters indicate corresponding componentsthroughout several views of the drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the presently contemplated best mode ofpracticing the invention is not to be taken in a limiting sense, but ismade merely for the purpose of describing the general principles of theinvention. The scope of the invention should be determined withreference to the claims.

Referring to FIG. 1, shown is a cross-sectional view of a carbonelectrode 100 including a foil collector 102, a first layer ofconducting carbon 104, and a second layer of activated carbon 106, inaccordance with one embodiment of the present invention.

All else being equal, the greater carbon quantity per unit volume thatcan be achieved within an electrochemical double layer capacitor, thegreater the capacitance of the electrochemical double layer capacitor.

This factor alone, however, would suggest that the ideal design for anelectrochemical double layer capacitor is a design in which two “chunks”of activated carbon juxtaposed against opposite sides of a porousseparator, and bracketed by terminal assemblies, one for each “chunk”,are employed to maximize the percentage of the volume of theelectrochemical double layer capacitor that is occupied by carbon, andminimize the percentage of the volume of the electrochemical doublelayer capacitor that is occupied by the porous separator and theterminal assemblies. This “brick sandwich” would then be immersed in anelectrolyte, and housed within an appropriate container.

Problematically however, it has also been found that the greater thelength an average electron (or hole) must travel through the carbon incharging or discharging the electrochemical double layer capacitor to agiven charge, the greater the internal resistance of the electrochemicaldouble layer capacitor, and thus the greater the RC time constant of theelectrochemical double layer capacitor.

This fact alone would suggest that the ideal design for anelectrochemical double layer capacitor is a design in which a largenumber of “specs” of activated carbon in an infinitely thin sheetjuxtaposed against opposite sides of one or more porous separators aresurrounded by large amounts of a highly conductive collector, so as tominimize the length an average electron (or hole) must travel throughthe carbon in charging or discharging the electrochemical double layercapacitor. This design would then be immersed in an electrolyte, andhoused within an appropriate container.

Neither of these extremes, however, is, in fact, ideal. Both the designof electrodes, and the design of the housing in which the electrodes,porous separator, and electrolyte are contained represent a balancebetween these two extremes, in order to both maximize capacitance, andat the same time minimize internal resistance of the electrochemicaldouble layer capacitor.

In order to achieve this objective, “effectivity” and “utilization” ofthe carbon used should be maximized by maximizing the surface area ofthe carbon used, minimizing the resistivity of the carbon used, and, atthe same time, maintaining pore size, and particle size (and thuspacking density) of the carbon that optimize both the “effectivity” and“utilization” of the carbon used.

The design of the present embodiment represents a significantimprovement over prior approaches because, in part, such design has asits object the above-referenced balance between maximizing carbon andminimizing internal resistance, and as its further object maximizing“effectivity” and “utilization” of the carbon.

The design begins with the electrodes, which, simplified, are asdepicted in FIG. 1. Each electrode consists of a thin metal collector102, onto which are formed two layers of carbon 104, 106, one on top ofthe other. The metal collector 102 serves both as a very low resistancecurrent path into and out of the carbon electrode 100, but also as amechanical platform for the two layers 104, 106.

The first layer 104, i.e., the layer in direct mechanical and electricalcontact with the thin metal collector 102, is of a “conducting carbon,”such as graphitic carbon (i.e., carbon having a laminar structure). Thisfirst layer 104 is approximately three times as conducting as the secondlayer 106, adheres well to both the thin metal collector 102 and thesecond layer 106, and provides low interfacial resistances between thethin metal collector 102 and the second layer 106. The first layer 104of conducting carbon (including binder used in the first layer 104)should also be stable in the electrolyte solution selected for use inthe electrochemical double layer capacitor.

The second layer 106 is of an “activated carbon,” and has surface area,pore size and particle size (packing density) characteristics, andFarads/cc and Farads/g that tend to maximize both the “efficiency” andthe “utilization” of the activated carbon. The second layer of activatedcarbon 106 should maximize capacitance, be stable (including binder usedin the second layer) in the electrolyte solution selected for use in theelectrochemical double layer capacitor, and should have low resistanceof the bulk.

The thin metal collector 102, or current collector 102 may be, forexample, an aluminum foil current collector. Foil suitable for thealuminum foil collector (foil collector 102) is available from All-FoilsIncorporated of Ohio as Al 1145 fully annealed to full hardened alloy,with a thickness of from between 12.5 to 50 micrometers, e.g., 1 mil,and a resistivity from between 2.83 to 2.87 micro ohms per centimeter.

The first layer 104 is formed onto the surface of the current collector102, and may comprise carbon powder such as, for example, Black Pearl2000, available from Cabot, of Billerica, Mass. Desirable properties ofthe first layer 104 are low resistivity, e.g., less than four ohms percentimeter; that the first layer 104 well to both the current collector102 (foil collector 102) and the activated carbon of the second layer106; low interfacial and sheet resistances between the conducting carbonand the current collector 102 (foil collector 102), and between theconducting carbon 104 and the activated carbon 106, e.g., less than fivemilliohms.

The second layer 106 is formed onto the first layer 104, and maycomprise activated carbon powder. The activated carbon powder used inthe carbon electrodes is used to provide high capacitance, due to high“effectivity” and “utilization.” A high capacitance is possible due, inpart, to the large BET surface area of the activated carbon powders,which is on the order of 500 to 2500 m²/g, e.g., 1900 m²/g for activatedcarbon, such as BP20, available from Kuraray Chemical of Japan. Surfacearea of the activated carbon powders is related to particle sizedistribution, which falls in the range of 3 to 30 μm with a d₅₀=8 μm. Awide range of particle sizes allows for an efficient packing density;small particles pack within the voids created by larger particles. Suchactivated carbon may be produced using starting materials such as kynel,rayon, coconut shell, or the like. Iodine absorption for such activatedcarbon may be, for example, 500 to 2500 mg/g, e.g., 2000 mg/g. Moisturecontent by a percentage of weight may be, for example, 0.2 to 0.7percent; ash content by weight may be, of example, 0.05 to 0.12 percent;particle diameter may be, for example, 3 to 30 nanometers; pore sizedistribution may be, for example, 60 to 500 nanometers, e.g., 60 to 300nanometers; capacitance may be, for example, 22 to 35 Farads per gram,e.g., 25 Farads per gram, i.e., for example, 15 to 20 Farads per cc.,e.g., 16 Farads per cc.

An important parameter in design optimization is Farads/cc—affecting“effectivity” and “utilization”. On a base materials level, this isaffected by the pore distribution, which typically ranges from 8 to 50Å. On an electrode level, the packing density of the powder comprisingthe electrodes determines Farads/cc. Carbon electrodes for the presentelectrochemical double layer capacitor application are fabricated with adesired electrode porosity (i.e., void to volume ratio) of 25% to 35%,which should be achieved through the selection of packing density anddrying conditions. The electrode porosity is optimized to maximizeparticle-to-particle contact, to lower the resistance, and facilitateelectrolyte permeation allowing for wetting of the carbon surfaces.

In order to further reduce the resistivity of the resultant electrode100, a small percentage (e.g., 1 to 5%) of conducting carbon, which ismore conducting than the activated carbon powder, such as Black Pearl2000, available from Cabot of Billerica, Mass., may be added to theslurry used to form the second layer 106.

A method of making the electrode 100 comprises applying powdered carbonin, for example, a slurry, a paste or a gel form (referred to generallyherein as a slurry form) onto current collector 102 (e.g., currentcollector plate 102 or foil 102, such as aluminum foils) or onto otherlayers already on the current collector. Such a slurry form of powderedcarbon may be made in a solution containing a polymer binder.

The binder may include, for example, polyvinylpyrrolidone; polyamide orthe like. Preferred binder may be Kynar 761 or Kynar 2801 available fromAtofina Chemicals of Pennsylvania. The binder should be insoluble in theselected electrolyte, for example, insoluble in acetonitrile; andsoluble in formulating solvents such as water, acetone, methyl ethylketone, N-methyl pyrolidone and the like. The binder should have avolume resistivity higher than 10⁹ ohms per centimeter, e.g., 2×10¹⁴ohms per centimeter; thermal decomposition at greater than 150 degreescentigrade, e.g., no less than 375 degrees centigrade, and wettabilitywith aluminum should be good.

Thus, the electrode 100 is made by applying a first layer of conductingcarbon 104 (with a binder in a slurry) to the current collector 102; anda second layer of activated carbon 106 (with a small amount ofconducting carbon, and with a binder in a slurry) to the first layer104.

Referring next to FIG. 2, a schematic diagram is shown illustratingslurry transfer apparatus and process 200 for applying carbon powderslurry 202, such as conducting carbon powder slurry or activated carbonpowder slurry, to a surface of a current collector 204 (or foil 204), soas to form the first layer of conducting carbon or the second layer ofactivated carbon on the surface of the foil.

Prior to the coating process, the surface of the foil 204 can be coronatreated, or mechanically or chemically modified, changing the surfaceenergy of the aluminum surface to promote wettability and adhesion.

In accordance with the present embodiment, the coating process proceedsin two steps. The first step involves applying a first layer (or primarycoating) to the bare aluminum surface of the foil 204 as a slurry 202containing a suitable binder (e.g., a water-based binder, such aspolyvinylpyrrolidone (PVP), ethylene acrylic acid (EAA); or asolvent-based binder, such as PVDF—“Kynar” 761 or “Kynar” 2801—availablefrom Atofina Chemicals of Philadelphia, Pa., and a suitable solvent,e.g. NMP, MEK, acetone or mixtures thereof). In addition, adhesionpromoters may be employed within the primary coating to improve theintegrity of the electrode without increasing the interfacialresistance. The proportion by weight of highly conducting carbon (versesother constituents, such as the binder and the solvent) included in theprimary coating preferably falls in the range of 25%-95%. The primarycoating preferably does not contain activated carbon.

The primary coating reduces the interfacial resistance and serves as aseed coat for a secondary coating.

The primary coating is applied using a slurry transfer apparatus andmethod 200, such as a reverse comma coat system and method, asillustrated. Other methods such as slot coating; gravure, extrusion,flexographic or roll coating methods may be used.

The reverse comma coat system and method 200 is illustrated. Shown is atransport roller 206, a transfer roller 208, and a carbon slurry roller210. Also shown is a set of wipers 212.

In practice the foil 204 passed between, the transport roller, and thetransfer roller. Spacing between the transport roller 206, against whichthe foil 204 is held tightly, and the transfer roller 208, determinesthe thickness of the primary coating. The carbon slurry 202, such asthat described above for use in applying the primary coating, isintroduced onto the carbon slurry roller 210, and carried to thetransfer roller 208. The carbon slurry 202 is then passed between thecarbon slurry roller 210 and the transfer roller 208. As a result, aportion of the carbon slurry 202 is transferred to the transfer roller208, and is then, in turn, transferred to one side of the foil 204.

Reverse comma coat methods and systems are well known, and thus furtherexplanation thereof is not made herein.

After the carbon slurry 202 is transferred to the one side of the foil204, the set of wipers 212 removes portions of the primary coating atedges of the foil 204, and at a center of the foil 204, for use increating contact edges and for assuring that a clean edge can be madeafter cutting and handling of the foil 204, as explained more fullybelow.

The second layer (or secondary coating) is applied over the primarycoating, either during a second pass through the reverse comma coatsystem 200, or in-line using a second reverse comma coat system. Ineither case, the secondary layer is applied after sufficient curing ofthe primary layer has taken place (by evaporation of the solvent), so asto maintain distinct primary and secondary layers.

The secondary coating comprises an activated carbon that is derived fromeither kynel, coconut or rayon base materials. As mentioned, thisactivated carbon has a high surface area, typically of the order of 1000to 2500 m²/g, in order to increase “effectivity”. The secondary coatingis applied using slurry comprising the high surface area activatedcarbon, a suitable binder (e.g., PVDF—“Kynar” 2801 available fromAtofina Chemicals of Philadelphia, Pa.) and a suitable solvent (e.g.NMP, MEK, acetone or a mixture thereof). The proportion by weight ofactivated carbon included in the secondary coating preferably, asopposed to other constituents (including binder and solvent), falls inthe range of 5% to 40%, e.g. approximately 30%. The secondary coatingmay also include a small amount of conducting carbon, such as theconducting carbon used in the first layer. The proportion by weight ofhighly conducting carbon included in the secondary coating preferablyfalls in the range of 0.01% to 5%, e.g., approximately 0.3%. This slurryis coated onto the primary carbon coat using the reverse comma coatprocess (or other process), as described above.

Although the process described above is an effective way of reducing theinterfacial and sheet resistance, the process steps involved becomesomewhat more complicated when coating of the foil 204 on both sides, asopposed to one side, is desired. To complete the coating of the foil204, in order to achieve a double-sided foil, the foil 204 goes throughthe reverse comma coat system and method 200 four times, once for eachof the first and second layers, on each of the first and second sides.

The reverse comma coat method and system 200 used to apply the secondarycoating are similar to those used to apply the primary coating,including the-use of the set of wipers 212 to remove portions of thesecondary coating at the edges and at the center of the foil 204. Thus,further separate explanation of the reverse comma coat system and method200 used to apply the secondary coating is not made herein.

Referring to FIG. 3, a top view is shown of the foil 302, the carbonpowder slurry 304, and the set of wipers 306 in a row that remove thecarbon powder slurry 304 from the foil 302 in three strips 308, 310, 312(or lanes 308, 310, 312) as the foil 302 passes through the slurrytransfer apparatus 200 of FIG. 2.

The three lanes 308, 310, 312 are located at the edges 314, 316 of thefoil 302, and at the center 318 of the foil 302, and are substantiallyfree of the carbon powder slurry 304. The outermost two of these threelanes 308, 312 are used to assure clean edges can be achieved at theedges 314, 316 of the foil 302 (without any curling, or bending that mayresult from handling of the foil 302 before, during or after theapplication of the first layer and the second layer). Furthermore, thesethree lanes 308, 310, 312 are used to create a contact edge (not shown)at one edge of the carbon electrode (explained more fully hereinbelow),whereby a low resistance electrical connection between a terminal andthe carbon electrode can be made.

Referring next to FIG. 4, a top view is shown of the foil 302 having thethree lanes 308, 310, 312 of the foil 302 (with the carbon powder slurryhaving been removed by the wipers of FIG. 3) separated by regions 402,404 coated with a first layer of conducting carbon and a second layer ofactivated carbon.

Also shown are four cut lines 406, 408, 410, 412 along which cuts in thefoil 302 are made after the first layer and the second layer have cured.

Cutting of the foil 302 along the four cut lines 406, 408, 410, 412 ispreferably achieved using a precision blade cutting apparatus (notshown), which may be in an apparatus separate from the slurry transferapparatus 200 (FIG. 2), or placed in-line with the slurry transferapparatus 200 (FIG. 2). Such cutting apparatus are known in the art, andthus further explanation thereof is not made herein. Cutting of the foil302 along the cut lines 406, 408, 410, 412 assures a clean edge for theelectrodes, results in the contact edge along one edge of eachelectrode, and cuts the foil 302 in half down its length, so as to formtwo electrodes. The contact edge provides a low resistance current pathbetween each terminal of the electrochemical double layer capacitor, anda respective electrode.

A first cut 410 is made down the center of the foil, and a second cut406 is made down a center of one of the lanes 308 at the edge of thefoil 302. A third cut 412 is made along one edge of the second region404 coated with the first and second layers, so as to remove the otherlane 312 at the edge of the foil 302, and a fourth cut 408 is made alonganother edge of the first region 402 coated with the first and secondlayers, so as to remove a remainder of the center lane 310 opposite theone edge of the foil 302.

As a result of the cutting of the foil 302, two identical separateelectrodes are formed, each having a contact edge, and a region coatedwith the first and second layers, the first being formed from half ofthe one lane 402 and the first region 402 coated by the first and secondlayers, and the second being formed from half of the center lane 310 andthe second region 404 coated by the first and second layers.

Numerous variations on the above-described embodiment for cutting thefoil 302 so as to form the first and second electrodes are contemplatedby the inventors and are within the scope of the present embodiment.

Referring to FIG. 5, a side cross-sectional view is shown of the foil ofFIG. 4 having the three lanes of the foil 302 separated by the regions402, 404 coated with the first layer of conducting carbon 502 and asecond layer of activated carbon 504.

As can be seen, the first layer 502 and the second layer 504 are coatedonto the foil 302, with the three lanes having been cleared of the firstlayer and the second layer by the set of wipers.

Also shown are the four cut lines 406, 408, 410, 412 along which thecuts in the foil 302 are made after the first layer 502 and the secondlayer 504 have cured. The four cuts are made along the four cut lines406, 408, 410, 412, as described above.

Referring to FIG. 6, a top view is shown of the foil 302 of FIG. 4having been cut into two foil electrodes 602, 604, such as the foilelectrode 100 in FIG. 1.

As can be seen, each of the two foil electrodes 602, 604 comprises theregion 402, 404 coated with the first layer of conducting carbon and thesecond layer of activated carbon; and the contact edge 602, 604.

Referring next to FIG. 7, a side cross-sectional view is shown of thetwo foil electrodes 602, 604 having their respective second layers 504of activated carbon juxtaposed against a porous separator 702, so as toform first and second carbon electrodes 602, 604 electrically (but notionically) isolated from one another by the porous separator 702.

The purpose of the porous separator 702 is to assure that the twospaced-apart carbon electrodes 602, 604 are never in direct electricalcontact with one another (as opposed to ionic flow, which is permittedby the porous separator 702).

The term “spaced-apart” is intended to refer to this lack of directelectrical contact between the electrodes 602, 604. A secondary purposeof the porous separator 702 is to enhance electrolyte solutionabsorption into the space between the two-spaced apart electrodes 602,604.

This purpose is important to the present embodiment, because contactbetween the two spaced-apart carbon electrodes 602, 604 would result ina short circuit and rapid depletion of the charges stored in theelectrochemical double layer capacitor 700.

Thus, provided the purpose of preventing direct electrical contactbetween the foil electrodes 602, 604 is fulfilled, a wide range ofmaterials and/or structures may be used as the porous separator 702,including, for example, mechanically spacing the two spaced apart carbonpowder electrodes 602, 604, without a physical barrier interposedbetween the two spaced apart carbon powder electrodes 602, 604.

The porous separator 702 may be, for example, TF3045 paper availablefrom Nippon Kodoshi Corporation of Japan. The porous separator 702,alternatively, may be made of polyethylene, polypropylene, other typesof paper, combinations or laminations thereof or the like. Thickness ofthe porous separator 702 may be, for example, from between 1 to 50micrometers, e.g., 35 micrometers; density may be, for example, frombetween 0.3 to 0.5 grams per centimeter cubed, e.g., 0.419 grams percentimeter cubed; tensile strength may be, for example, greater than 10Newtons per 15 millimeters, e.g., 12.7 Newtons per 15 millimeters;porosity may be, for example, 40 to 80 percent, e.g., 72 percent;electrolyte absorbency, for example, 10 to 80 millimeters per 10minutes, e.g., 39 millimeters per 10 minutes; and thermal stability maybe −55 degrees Celsius to 150 degrees Celsius.

In accordance with a preferred embodiment, the illustrated componentsare compressed against each other with a modest constant pressure, withthe porous separator 702 preventing an electrical short, i.e., directelectrical contact, between the foil electrodes 602, 604.

In practice, all of the available spaces and voids within and betweenthe two carbon electrodes 602, 604 (tow foil electrodes 602, 604) arefilled with a highly conductive, preferably non-aqueous electrolytesolution, such as tetra ethylammonium tetra fluoriborate (Et₄NBF₄)(TEABF₄) salt with acetonitrile (CH₃CN) as a solvent.

Other possible salts include Triethyl methyl ammonium and other alkylammonium salts.

Other possible solvents include propylene carbonate (PC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), dimethyl carbonate (DMC),methyl formate and their mixtures.

It is to be emphasized, that the invention herein described contemplatesthe use of alternate electrolyte solutions, particularly non-aqueous (ororganic) electrolyte solutions, other than the solution made fromacetonitrile described above.

The electrolyte solution should preferably have a conductivity of, e.g.,from between 10 to 100 milli-Siemens, e.g., 66 milli-Siemens; aliquidous range of, e.g., from between −55 to 200 degrees Celsius, e.g.,−55 to 87 degrees Celsius; and a voltage range of greater than 2 volts.

The ions of the electrolyte solution are free to pass through pores orholes of the porous separator; yet, as mentioned above, the separatorprevents the one electrode from physically contacting, and henceelectrically shorting with, the other electrode.

In operation, when an electrical potential is applied across the contactedges of the carbon electrodes, and hence across the carbon electrodes602, 604, a polarized liquid layer forms at the surface of eachelectrode immersed in the electrolyte. It is this polarized liquid layerthat stores electrostatic energy and functions as the double layercapacitor—i.e., that functions as two capacitors in series.

More specifically, when a voltage is applied across the carbonelectrodes 602, 604, e.g., when one electrode 602 is charged positiverelative to the other electrode 604, a polarized liquid layer is formedby the polarization of the electrolyte ions due to charge separationunder the applied electric field and also due to the dipole orientationand alignment of electrolyte molecules over the entire surface of theelectrodes 602, 604. This polarization stores energy in the capacitoraccording to the following relationships:

 C=k _(e) A/d  (1)

andE=CV ²/2  (2)where C is the capacitance, k_(e) is the effective dielectric constantof the double layer, d is the separation distance between the layers, Ais the surface area of the foil electrodes 602, 604 that are immersed inthe electrolyte solution, V is the voltage applied across the foilelectrodes 602, 604, and E is the energy stored in the electrochemicaldouble layer capacitor 702.

In the present embodiment, the separation distance d is so small that itis measured in angstroms, while the surface area A, i.e., the surfacearea “A” per gram of electrode material, is very large. Hence, as can beseen from Eq. (1), when d is very small, and A is very large, thecapacitance is very large.

The surface area “A” in the electrochemical double layer capacitor 702is large because of the makeup of the foil electrodes 602, 604.Specifically, each of the foil electrodes 602, 604 comprises activatedcarbon powders in the secondary coating 504, respectively. Activatedcarbon is a highly porous form of carbon. The activated carbon powdersdo not have a smooth surface, but are pitted with numerous pores. Thepores of the activated carbon powders have a typical size of about 5 to40 Å (Angstroms).

The carbon electrodes 602, 604 are immersed in the electrolyte solution.Each hole and pore increases the surface area of the powder that isexposed to the electrolyte solution. The result is a three-dimensionalelectrode structure which allows the electrolyte to penetrate into thepores, and contact all, or most all, of the surface area of the carbonpowders, thereby dramatically increasing the surface area “A” of theelectrode over which the double layer of charged molecules is formed.

Achieving a high capacitance, however, is only one aspect of the presentembodiment. As noted above, another important aspect of the presentembodiment is that the electrochemical double layer capacitor is capableof storing and discharging energy in a relatively quick time period,i.e., the RC time constant of the electrochemical double layer capacitor702 is relatively small, e.g., on the order of less than 1 second, e.g.,0.5 seconds.

The internal resistance of the electrochemical double layer capacitor702 is made up of several components. Specifically, the internalresistance components include a contact resistance R_(C), an electroderesistance R_(EL), an electrolyte solution resistance R_(ES), and aseparator resistance R_(SEP).

The contact resistance R_(C) represents all of the resistance in thecurrent path from the capacitor terminal (not shown) up to the contactedge of the carbon electrode 602, 604. The electrode resistance R_(EL)represents the resistance within the electrodes 602, 604. Theelectrolyte solution resistance R_(ES) exists relative to theelectrolyte solution, and the separator resistance R_(SEP) existsrelative to the porous separator 702.

The forgoing description has focused principally on teachings of thepresent embodiment directed to minimizing the electrode resistanceR_(E1), although the electrolyte solution and the porous separator 702,described above, are selected to minimize the electrolyte solutionresistance R_(ES) (balanced against the voltage that the electrolytesolution will tolerate, as described further herein below) and separatorresistance R_(SEP), respectively. Description hereinbelow, beginning inreference, for example, to FIG. 12 is directed to teachings forminimizing contact resistance R_(C).

Any energy stored within the electrochemical double layer capacitor 700enters or exits the capacitor by way of an electrical current that flowsthrough R_(C), R_(EL), R_(ES), and R_(SEP). Thus it is seen that inorder for practical charge/discharge times to be achieved, the values ofR_(C), R_(EL), R_(ES), and R_(SEP), which in combination with thecapacitance C define the time constant t_(C) of the capacitor 100, arepreferably kept as low as possible.

The resistance of the porous separator R_(SEP) is a function of theporosity and thickness of the porous separator 702.

The resistance of the electrolyte solution R_(ES) is a function of theconductivity of the particular electrolyte solution used. In selectingthe type of electrolyte solution, several tradeoffs are considered.Aqueous electrolyte solutions generally have a higher conductivity thando non-aqueous solutions (e.g., by a factor of 10). However, aqueoussolutions limit the working voltage of the capacitor cell to around 1.0volt. Because the energy stored in the cell is a function of the squareof the voltage, high-energy applications are better served using anon-aqueous electrolyte, which permit cell voltages on the order of 2.0to 3.0 volts.

The preferred electrolyte, a mixture of acetonitrile (CH₃CN) and asuitable salt, exhibits a conductivity on the order of 60 ohm⁻¹ cm⁻¹.

A result of the present embodiment is that R_(C)+R_(EL) are reduced to avalue that is small in comparison to R_(SEP)+R_(ES).

Referring to FIG. 8, a side cross-sectional view is shown of the foil302 of FIG. 4 wherein both first and second sides 802, 804 of the foil302 include regions 806, 808, 810, 812 having the first layer ofconducting carbon 814 and the second layer of activated carbon 816, andfurther include the three lanes 308, 310, 312 of the foil 302 separatedby the regions 806, 808, 810, 812 coated with the first layer ofconducting carbon 814 and a second layer of activated carbon 816.

The embodiment of FIG. 8 is identical to the embodiment of FIGS. 5 and7, except that instead of having the first layer 814 and the secondlayer 816 (and the three lanes of foil 308, 310, 312 without the firstlayer 814 and the second layer 816) on only one side of the foil, thefirst layer 814 and the second layer 816 are formed on both sides 802,806 of the foil 302, effectively doubling the amount of carbon presentin the foil electrode, and thereby increasing the capacitance of theelectrochemical double layer capacitor.

The foil 302 of FIG. 8 is made in accordance with the process describedabove in reference to FIGS. 2 through 4, except that the foil 302 passesthrough the slurry transfer apparatus 200 (FIG. 2) two additional times(or passes through two additional slurry transfer apparatus, inline withan initial two slurry transfer apparatus 200) so that a total of fourlayers of carbon are deposited onto the foil 302, two layers 814, 816 oneach side 802, 804. The foil 302 is inverted after the first layer 814and the second layer 816 are formed on the first side 802, so that afirst layer 814 and a second layer 816 can be formed on the second side804 of the foil 302.

Alternatively, the foil 302 may be inverted after the first layer 814 isformed on the first side 802, so that the first layer 814 on the secondside 804 can be formed; thereafter the foil 302 is inverted again sothat the second layer 816 can be formed on the first side 802; and,finally, the foil 302 is again inverted so that the second layer 816 onthe second side 804 can be formed.

The foil 302, having a first layer 814 and a second layer 816 on eachside 802, 804 is then cut along the cut lines 406, 408, 410, 412depicted, as described above in reference, for example, for FIGS. 4through 6.

Other possible methods of making the carbon electrodes include employingperforated foil collector plates or screens (not shown). The carbonslurry may be coated onto the perforated foil collector plates orscreens through an extrusion process using a die, thus enabling thecoating process to be completed in two steps (one for the first layer onboth sides of the perforated foil collector plates or screens, andanother for the second layer on both sides of the perforated foilcollector plates or screens), minimizing the number of process stepsthus lowering cost.

Referring next to FIG. 9, a side cross-sectional view is shown of fourfoil electrodes 902, 904, 906, 907 such as in FIG. 8, having first andsecond sides 908, 910, 912, 914, 916, 918, 917, 919 including the firstlayer of conducting carbon 920 and the second layer of activated carbon922, with the second layer of activated carbon 922 of first and secondones of the foil electrodes 902, 904 juxtaposed against respective sides924, 926 of a first porous separator 928; another second layer ofactivated carbon 922 of second and third ones of the foil electrodes904, 906 juxtaposed against respective sides 930, 932 of a second porousseparator 934; and a further second layer of activated carbon 922 offirst and fourth ones of the foil electrodes 902, 907 juxtaposed againstrespective sides 931, 933 of a third porous separator 935 so as to formfirst, second, third and fourth carbon electrodes 902, 904, 906, 907electrically (but not ionically) isolated from one another by the first,second and third porous separators 928, 934, 935.

The four foil electrodes 902, 904, 906, 907 and the porous separators928, 934, 935 are immersed in the electrolyte solution, and functionsimilarly to the foil electrodes 602, 604 separator 702 and electrolytesolution described in reference, for example, to FIG. 7. Note, however,that the first and third ones of the foil electrodes 902, 906, havetheir contact edges 936, 938 (to the right as depicted) electricallyconnected, i.e., shorted (not shown), so that such first and third onesof the foil electrodes 902, 906 serve as one electrode of theelectrochemical double layer capacitor 900, and the second and forthones of the foil electrodes 904, 901 have their contact edges 940, 941(to the left as depicted) electrically connected, i.e., shorted (notshown), so that such second and fourth ones of the foil electrodes 904,901 serve as another electrode of the electrochemical double layercapacitor 900.

Referring to FIG. 10, a partial top view is shown illustrating windinglayers comprising a pair of the carbon electrodes 1002, 1004, such as inFIG. 8, having first and second sides including the first layer ofconducting carbon and the second layer of activated carbon, and beingseparated by the first and second porous separators 1006, 1008.

Shown is a first foil electrode 1002, a first separator 1006, a secondfoil electrode 1004, and a second separator 1008. As can be seen, thefirst foil electrode 1002 and the second foil electrode 1004, e.g., thepositive foil electrode 1002 and the negative foil electrode 1006, areoffset from the first separator 1006 and the second separator 1008, andare positioned on opposite sides, e.g., top and bottom sides, of thefirst separator. (This difference in width and the relationship betweenthe foil electrodes and the separators can also be seen in FIG. 9.) Thesecond separator 1008 is positioned under the second foil electrode 1004so that when the first and second separators 1006, 1008, and the firstand second foil electrodes 1002, 1004 are rolled together, oppositesides of the first and second separators 1006, 1008 provide insulationbetween adjacent sides of the first foil electrode 1002 and the secondfoil electrode 1004.

Advantageously, the first and second foil electrodes 1002, 1004 aredouble sided, as depicted in FIG. 8, in that they have been coated withthe first and second layers on both sides. In this way, the amount ofcarbon in each electrode is effectively doubled.

When the first foil electrode 1002 is placed against the firstseparators 1006, a portion 1010 of a contact edge 1012 of the first foilelectrode 1002 extends beyond a first edge 1014 of the first and secondseparators 1006, 1008. The portion 1010 of the contact edge 1012 of thefirst foil electrode 1002 may be, for example, 0.125 inches wide, whilethe contact edge 1012 of the first foil electrode 1002 may be, forexample, 0.250 inches wide.

At the same time, a portion 1016 of the first and second porousseparators 1006, 1008 at an opposite edge 1018 of the first and secondporous separators 1006, 1008 extends beyond the first foil electrode1002 in order to prevent shorting of the first foil electrode 1002 witha contact edge 1020 of the second foil electrode 1004. The portion 1016of the first and second separators 1006, 1008 may be, for example, 0.125inches wide.

A portion 1022 of the contact edge 1020 of the second foil electrode1004 extends beyond the opposite edge 1018 of the first and secondseparators 1006, 1008, e.g., by 0.125 inches, and a portion 1022 of thefirst and second porous separators 1006, 1008 at the opposite edge 1018of the first and second porous separators 1006, 1008 extends beyond thesecond foil electrode 1004, e.g., by 0.125 inches, in order to preventshorting of the second foil electrode 1004 with the contact edge 1012 ofthe first foil electrode 1002. The contact edge 1020 of the second foilelectrode 1004 may be, for example, 0.250 inches wide.

Portion 110, 1022 of the contact edges 1012, 1020 of the first foilelectrode 1002 and second foil electrode 1004 that extend beyond thefirst and second (or opposite) edges 1014, 1018, respectively, of thefirst and second separators 1006, 1008 serve as points of contact forthe first foil electrode 1002 and second foil electrode 1004,respectively.

FIG. 11 is an end, assembly cross-sectional view of a “jellyroll”electrode assembly 1100 comprising a pair of the carbon electrodes 1102,1104, such as in FIG. 8, having first and second sides including thefirst layer of conducting carbon and the second layer of activatedcarbon, and being separated by first and second porous separators 1106,1108 in accordance with a “jellyroll” embodiment employing the windinglayers of FIG. 10.

Shown is the first foil electrode 1102, the second foil electrode 1104,the first separator 1106, and the second separator 1108. As can be seen,layers comprising the first separator 1106, the first foil electrode1102, the second separator 1108, and the second foil electrode 1106 arerolled in a “jellyroll” fashion such that each of two coated surfaces ofthe first foil electrode 1102 and the second foil electrode 1104 areseparated by the first and second separators 1106, 1108, respectively,thereby maximizing surface area per unit volume and maximizingcapacitance.

The two foil electrodes 1102, 1104 are offset (as described furtherhereinabove, so as to leave their respective contact edges extendingbeyond first and second edges of the first and second separators 1106,1108) and assembled into a jellyroll configuration electricallyseparated from each other by the first separator 1106 and the secondseparator 1108, which can be a polymer film or paper.

Preferably, the first separator 1106 and the second separator 1108extend beyond ends of the first electrode 1102 and the second electrode1104 (as described further hereinabove), to prevent “shorting,” i.e.,electrical current from flowing between the first foil electrode 1102and the second foil electrode 1104.

Referring next to FIG. 12, a perspective view is shown of the“jellyroll” electrode assembly 1200 of FIG. 11 including with aluminumarc sprayed regions 1202, 1204 at an end 1016 of the “jellyroll”electrode assembly 1200 so as to provide a low resistance path between acontact edge 1208 of the first carbon electrode, and includingadditional arc sprayed regions (not shown) at an opposite end of the“jellyroll” electrode assembly 1200 so as to provide another lowresistance path between contact edges of the second carbon electrode.

Shown is the “jellyroll” electrode assembly 1200, the second separator,the contact edge 1208 of the first foil electrode, the contact edge ofthe second foil electrode, a first aluminum region 1202 and a secondaluminum region 1204 on the contact edge 1208 of the first foilelectrode.

The “jellyroll” electrode assembly 1200 is formed by winding or rollingthe first foil electrode, the second foil electrode, the firstseparator, and the second separator, as described hereinabove.

Once the “jellyroll” electrode assembly 1200 is formed, the contact edge1208 of the first electrode and the contact edge of the second electrodeare “smeared” by applying a slight pressure against the respectivecontact edges, both axially and radially toward a center of the“jellyroll” electrode assembly 1200. As a result of this “smearing” thecontact edges are bent radially toward a center 1210 of the “jellyroll”electrode assembly 1200, which tends to expose surfaces of the contactedges 1208 and to close gaps between windings at the contact edges 1208.

Once “smearing” of the contact edges 1208 is complete, the first end1206 and second end 1212 of the “jellyroll” electrode assembly 1200 aremasked, so that two sectors of each of the first and second ends 1206,1212 are exposed, while a remainder of the first and second ends 1206,1212 are masked. The two sectors extend from an outside corner edge ofthe “jellyroll” electrode assembly 1200 and extend radially about twothirds of the way to a center axis 1210 of the “jellyroll” electrodeassembly 1200. Each sector is about 45° wide.

Once the first end 1202 of the “jellyroll” electrode assembly 1200 aremasked, the first end 1206 is arc sprayed with aluminum or anotherelectrically conductive material compatible with the electrolytesolution. Once the arc spraying is complete, the masks are removed fromthe first end 1206. One purpose of the arc spraying of the first end1206 of the “jellyroll” electrode assembly 1200 is to provide a lowresistance current path between windings (i.e., between contact edges)of the first foil electrode, thus reducing overall electrode resistance.

First and second aluminum regions (not shown) are also formed at thesecond end of the “jellyroll” electrode assembly in a manner similar tothat in which first and second aluminum regions 1202, 1204 are formed atthe first end of the “jellyroll” electrode assembly 1200, providing alow resistance current path between windings (i.e., between contactedges of the second electrode, thus further reducing overall electroderesistance.

In order to create a low resistance contact, a collector disk (notshown) and a terminal post (not shown) are aligned with and placedagainst each of the ends of the “jellyroll” electrode assembly 1200 soas to place the collector disk into electrical contact with the contactedges of the foil electrode at the respective end of the “jellyroll”electrode assembly 1200, and with the first and second aluminum regions1202, 1204 at the respective end of the “jellyroll” electrode assembly1200.

The collector disk is then attached to the end of the “jellyroll”electrode assembly 1200 at the first and second aluminum regions bylaser welding, thus providing a low resistance contact between the endof the “jellyroll” electrode assembly 1200 and the terminal assembly. Asa result, a low resistance contact is provided between the first foilelectrode and the first terminal assembly and the second foil electrodeand the second terminal assembly.

Alternatively, the first terminal assembly and the second terminalassembly may be aligned with and placed against the ends of the“jellyroll” electrode assembly 1200 prior to the formation of the firstand second aluminum regions, in which case the arc spraying of the firstand second aluminum regions serves to “weld” the collector disks intoelectrical contact with the contact edges of the first and second foilelectrodes.

In one variation, when the collector disks are seated against thealuminum coated regions of the ends of the “jellyroll” electrodeassembly 1200, and when the amount of aluminum at the aluminum coatedregions is sufficient to raise the collector disks above remainingcontact edges of the ends of the “jellyroll” electrode assembly 1200,thereby creating a small gap between the collector disks and the contactedges, this allows the electrolyte solution to flow beneath thecollector disks and then to flow between the windings of the “jellyroll”electrode assembly 1200 that lie beneath the collector disks.

Preferably, however, the collector disks are seated against both thecoated regions and the uncoated regions of the ends of the “jellyroll”electrode assembly 1200, with sufficient electrolyte solution beingpermitted to flow between the collector disks and the ends of the“jellyroll” electrode-assembly 1200 to permit the electrolyte solutionto flow between the windings of the “jellyroll” electrode assembly 1200that lie between the collector disks.

Referring to FIG. 13, a side cross-sectional view is shown of the“jellyroll” electrode assembly 1200 of FIG. 12, having the windinglayers of FIG. 11.

Shown is the “jellyroll” electrode assembly 1200 made up of thewindings, the contact edge 1302 of the first foil electrode, the contactedge 1304 of the second foil electrode, and a hollow core 1306.

In order to form the “jellyroll” electrode assembly's winding layers,the first and second foil electrodes, and the first and secondseparators, as described herein, are wound, as described herein.

Referring to FIG. 14, is a side cross-sectional view of the “jellyroll”electrode assembly 1200 of FIG. 12, having the winding layers of FIG.11, and further having a first stud 1402 (or plug 1402), and a firstcollector disk 1404.

Shown are the windings, the contact edge 1302 of the first foilelectrode, the contact edge 1304 of the second electrode, the hollowcore 1306, and the first stud 1402, and the first collector disk 1404.

The first stud 1402 is aligned with a first end of the hollow core 1306,and is inserted into an opening at the end of the hollow core 1306, athreaded post 1406 extends from the stud 1404, away from the hollow core1306.

When the stud 1402 is inserted into the opening at the end of the hollowcore 1306, the first collector disk 1404 seats against the first end ofthe “jellyroll” electrode assembly 1200 including the first and secondaluminum regions of the first end of the “jellyroll” electrode assembly1200, and is laser welded to the first end of the “jellyroll” electrodeassembly 1200, including the first and second aluminum regions of thefirst end of the “jellyroll” electrode assembly 1200.

Referring next to FIG. 15, a side cross-sectional view is shown of the“jellyroll” electrode assembly 1200 of FIG. 12, having the windinglayers of FIG. 11, and the first plug 1402 of FIG. 14, and furtherhaving a remainder of a first terminal assembly 1502.

Shown are the windings, the contact edge 1302 of the first foilelectrode, the contact edge 1304 of the second foil electrode, thehollow core 1306, the first stud 1402, a first collector disk 1404, afirst terminal post 1504, and a lid 1506.

The lid 1506 is welded to the first terminal post 1504, which includes asocket, which may be, for example, threaded and formed at a base of thefirst terminal post 1504. Next, a hole in a center at the collector diskis placed over the threaded post of the first stud 1402, and the firstterminal post 1504 is coupled to the threaded post on the first stud1402 at the socket, such as be screwing the first terminal 1504 postonto the first stud 1402, thereby interposing the collector disk 1404between the first stud 1402 and the first terminal post 1504.

The first terminal post 1504 (and second terminal post, described below)may have a diameter of approximately 0.625 inches.

Referring to FIG. 16, a side cross-sectional view is shown of the“jellyroll” electrode assembly 1200 of FIG. 12, having the windinglayers of FIG. 11, the first plug 1402 of FIG. 14 and the remainder of afirst terminal assembly 1502 of FIG. 15, and further having a secondplug 1602 (or stud 1602), a second collector disk 1604 and a secondterminal post 1606.

Shown is the “jellyroll” electrode assembly's windings, the contact edge1302 of the first foil electrode, the contact edge 1304 of the secondelectrode, the hollow core 1306, the first stud 1402, the firstcollector disk 1404, the first terminal post 1504, the lid 1506, thesecond stud 1602, the second collector disk 1604, and the secondterminal post 1606.

The second stud 1602 includes a threaded post onto which a hole in acenter of the second collector disk 1604 is placed, and to which thesecond terminal post 1606 is coupled, such as by screwing a threadedsocket of the second terminal post 1606 onto the second stud 1602. Thesecond stud/collector disk/terminal post 1602/1604/1606 is aligned witha second end of the hollow core 1306.

The second stud 1502 is then inserted into an opening at the second endof the hollow core 1306, and the second collector disk 1604 is seatedagainst the second end of the “jellyroll” electrode assembly 1200including the first and second aluminum regions of the second end of the“jellyroll” electrode assembly 1200. The second collector disk 1604 islaser welded to the second end of the “jellyroll” electrode assembly1200, including the first and second aluminum regions of the second endof the “jellyroll” electrode assembly 1200.

Referring to FIG. 17, a side, exploded cross-sectional view is shown ofthe “jellyroll” electrode assembly 1200 of FIG. 12, having the windinglayers of FIG. 11, the first plug 1402 of FIG. 14, the remainder of thefirst terminal assembly 1502 of FIG. 15 and the second plug 1602, thesecond collector disk 1504 and the second terminal post 1602 of FIG. 16,and further having a first insulating washer 1702, and a can 1704.

Shown is the “jellyroll” electrode assembly 1200 the contact edge 1302of the first foil electrode, the 1304 contact edge of the second foilelectrode, the hollow core 1306, the first stud 1402, the firstcollector disk 1404, the first terminal post 1504, the lid 1506, thesecond stud 1602, the second collector disk 1604, the second terminalpost 1602, a first insulating washer 1702 and a can 1704.

The first insulating washer 1702 is placed over the second terminal post1606. The first insulating washer 1702 may be made from Tefzel. Next,the can 1704 is slid over the “jellyroll” electrode assembly 1200 sothat the second terminal post 1606 enters the can 1704 first. The can1704 may be made, for example, from aluminum and have a wall thicknessof 0.4 inches. The diameter of the can 1704 may be for example 2.5inches, and the length of the can may be for example 6 inches. Next, thesecond terminal post 1606 passes through an axial hole 1706 at an end ofthe can 1704. A flange on the first insulating washer 1702 preventselectrical contact between the second terminal post 1606 and the axialhole 1706.

Simultaneously, the lid 1506 is drawn into the opening of the can 1704,so that a rim of the lid 1506 sits just inside a lip of the opening ofthe can 1704. The rim of the lid 1506 is then welded to the lip of theopening of the can 1704.

Referring next to FIG. 18, a partial side cross-sectional view is shownof the second terminal post 1606 of FIG. 16, and the first insulatingwasher 1702, and the can 1704 of FIG. 17, and further having a secondinsulating washer 1802, a flat washer 1804, a Belleville washer 1806 anda locknut 1808.

After the second terminal post 1606 passes through the axial hole 1706(FIG. 17) at an end of the can 1704, the second terminal post 1606passes through the second insulating washer 1802. The second insulatingwasher 1802 may also be made from Tefzel. The second terminal post 1606next passes through the flat washer 1804, and the Belleville washer1806. The locknut 1808 is then tightened over the Belleville washer1806, which compresses the Belleville washer 1806 against the flatwasher 1804, which in turn is compressed against the second insulatingwasher 1802. The second insulating washer 1802 is compressed against anexterior periphery of the axial hole 1706 (FIG. 17) in the can 1704, andas the second terminal post 1606 is drawn by this compressive forcetoward the axial hole 1706 (FIG. 17), the first insulating washer 1702is compressed between the second terminal post 1606 and an interiorperiphery of the axial hole.

Referring to FIG. 19, partial side cross-sectional view of the“jellyroll” electrode assembly 1200 of FIG. 12, having the windinglayers of FIG. 11, the first plug 1402 of FIG. 14, the remainder of thefirst terminal assembly 1502 of FIG. 15, the second plug 1602, thesecond collector disk 1604 and the second terminal post 1606 of FIG. 16,the first insulating washer 1702, and the can 1704 of FIG. 17, thesecond insulating washer 1802, the flat washer 1804, the Bellevillewasher 1806 and the locknut 1808 of FIG. 18.

As can be seen, the first insulating washer 1702 and the secondinsulating washer 1802, including the flange of the first insulatingwasher, serve to insulate the second terminal post 1606 from the can1704. The flat washer 1804, and the Belleville washer 1806 arecompressed against the second insulating washer 1802 by the locknut1808, as the second terminal post 1606 is drawn through the hole in thecan 1706 to form an hermetic seal between the second terminal post 1606,the first insulating washer 1702, the second insulating washer 1802 andthe can 1704. The Belleville washer 1806 assures that this seal ismaintained through thermal cycling by providing a spring force againstthe flat washer 1804 and the locknut 1808.

Referring to FIG. 20, a perspective view is shown of an electrochemicaldouble layer capacitor 2000 made in accordance with the “jellyroll”embodiment of FIG. 19.

Once the locknut 1808 (FIG. 18) is tightened against the Bellevillewasher 1806 (FIG. 18), as described above, a hermetic seal is formedbetween the hole 1706 (FIG. 17) in the can 1704, the first insulatingwasher 1702 (FIG. 18), the second insulating washer 1802 (FIG. 18), andthe second terminal post 1606. Similarly, the welding of the lid 1506 tothe lip 2002 of the can 1704, and the welding of the lid 1506 to thefirst terminal post 1504 form another hermetic seal.

A hole 1902 in the lid 1504, however, remains, and serves as a fill portfor an electrolyte solution.

In accordance with the present embodiment, the electrolyte solution maybe made up of a solvent and a salt. A preferred solvent is acetonitrile(CH₃CN) and preferred salts include 1.4 M tetraethyl ammonium tetrafluroborate. Other salts may be used, such as, triethyl ammonium, and otheralkyl ammonium salts. Other solvents may include propylene carbonate,ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, methylformate, and combinations thereof. Preferred electrolyte has aconductivity of from between ten and one hundred milli-Siemens, e.g., 66mS, a liquidus range of −55 to 200, e.g., −55 to 87 degrees Celsius anda voltage range of greater than 2 volts.

The electrolyte solution is added to the can 1704 through the hole 1902.Evacuation of the can 1704 can be performed prior to the adding of theelectrolyte solution, so that the electrolyte solution is drawn(backfilled) into the can and into the jellyroll electrode assembly 1200(FIG. 13). In particular, the electrolyte solution is drawn into theporous surfaces of the first foil electrode and the second foilelectrode made up of the first layer of conductive carbon, and thesecond layer of activated carbon. Some settling of the electrolytesolution may result in a need for additional electrolyte solution to beadded before a plug 2004 and bushing 2006 are inserted into the lid1506.

The bushing 2006 is then placed into the hole 1902, and is seatedagainst a flange (not shown) at an interior edge of the hole 1902. Thebushing 2006 is a hollow cylinder in shape. Next, the plug 2004, whichis cylindrical in shape is pressed into a center of the bushing 2006,which presses the bushing 2006 against an interior of the hole 1902,thereby forming a hermetic seal between the hole 1902, bushing 2006, andplug 2004.

Advantageously, the plug 2004 and bushing 2006 may be selected todislodge when a prescribed level of pressure is reached within the can1704, thereby providing an overpressure safety mechanism.

Shown are the first terminal post 1504, the lid 1506, the can 1704, thehole 1706 in the lid 1506, the bushing 2006, and the plug 2004. Also,shown is the second terminal post 1606.

Referring next to FIG. 21, a side cross-sectional view is shown of avariation of the “jellyroll” embodiment of FIGS. 12 through 20, havingan improved collector plate, and a reduced number of parts in a firstterminal assembly 2102, and a second terminal assembly 2104.

An electrochemical double layer capacitor made in accordance with theabove-described embodiment may have a capacitance of about 2,650 to2,700 Farads, with an impedance less than 0.6 milli-ohms.

Shown is the “jellyroll,” windings 2106 of the “jellyroll” electrodeassembly 2108, the contact edge 2110 of the first foil electrode, thecontact edge 2112 of the second foil electrode, the hollow core 2114, afirst stud/collector disk 2114, the first terminal post 2116, the lid2118, the second stud/collector disk/terminal post 2120, the can 2122, afirst insulating washer 2124, a second insulating washer 2126, a flatwasher 2128, a Belleville washer 2130, and a locknut 2132.

In order to form the “jellyroll” windings 2106 comprising the first andsecond foil electrodes, and the first and second separators, asdescribed hereinabove, the “jellyroll” windings 2106 are wound, asdescribed hereinabove.

The first stud/collector disk 2114 comprises a disk-shaped portion 2134,a stud portion 2136, and a fastener 2138, such as a screw, formed as asingle integral piece. The first/stud collector 2114 is aligned with thefirst end of the hollow core 2112, and the stud portion 2136 of thefirst stud/collector disk 2114 is inserted into an opening at the firstend of the hollow core 2112.

When a stud portion 2136 of the first stud/collector disk 2114 isinserted into the opening at the first end of the hollow core 2112, thedisk-shaped portion 2134 (or collector disk portion 2134) of thefirst/stud collector disk 2114 seats against the first end of the“jellyroll” electrode assembly 2108 including first and second aluminumcoated regions (similar to those shown in FIG. 12) on the first contactedge 2110 of the first end of the “jellyroll” electrode assembly 2114,and is laser welded to the first and second aluminum regions and thefirst contact edge 2110 of the first end of the “jellyroll” electrodeassembly 2108.

The lid 2118 is then welded to the first terminal post 2116, and asocket, which may be for example, threaded, is coupled to the fastener2138 on the first stud/collector disk 2114, such as by screwing thefirst terminal post 2116 onto the first stud/collector disk 2114.

Next, the second stud/collector disk/terminal post 2120 is aligned withthe second end of the hollow core 2112 and the second stud/collectordisk/terminal post 2020 is aligned therewith. The second stud/collectordisk/terminal post 2120 includes a stud portion 2140, a disk-shapedportion 2142 (or collector disk portion 2142), and a terminal postportion 2144 (or second terminal post 2144). The stud portion 2140 ofthe second stud/collector disk/terminal post 2020 is inserted into anopening at a second end of the hollow core 2112, and the collector diskportion 2142 of the second stud/collector disk/terminal post 2020 isseated against the second end of the “jellyroll” electrode assembly 2108including the first and second aluminum regions (similar to those shownin FIG. 12) and second contact edge 2112 of the second end of the“jellyroll” electrode assembly 2108. The collector disk portion 2142 ofthe second stud/collector disk/terminal post 2120 is laser welded to thesecond end of the “jellyroll” electrode assembly 2108 including thefirst and second aluminum regions and the second contact edge 2112 ofthe second end of the “jellyroll” electrode assembly 2108.

The can 2122 is then slid over the “jellyroll” electrode assembly 2108so that the second stud/collector disk/terminal post 2120 enters the can2122 first, and passes through the first insulating washer 2124. Thefirst insulating washer 2124 may be made from Tefzel. Next, the secondstud/collector disk/terminal post 2120 passes through an axial hole atan end of the can 2122 and through the second insulating washer 2126.The second insulating washer 2126 may also be made from Tefzel.

The second stud/collector disk/terminal post 2120 next passes throughthe flat washer 2128 and the Belleville washer 2130. The locknut 2132 isthen tightened over the Belleville washer 2130, which compresses theBelleville washer 2130 against the flat washer 2128, which in turn iscompressed against the second insulating washer 2126. The secondinsulating washer 2126 is compressed against the exterior periphery ofthe axial hole in the can 2122, and as the second stud/collectordisk/terminal post 2120 is drawn by this compressive force toward theaxial hole, the first insulating washer 2124 is compressed between thesecond stud/collector disk/terminal post 2120 and an interior peripheryof the axial hole in the can 2122. A flange on the first insulatingwasher 2124 prevents electrical contact between the secondstud/collector disk/terminal post 2120 and a rim of the axial hole.

Simultaneously, the lid 2118 is drawn into an opening of the can 2122,so that a rim of the lid 2118 sits just inside a lip of the opening ofthe can 2122. The rim of the lid 2118 is then welded to the lip of theopening of the can 2122.

Once the locknut 2132 is tightened against the Belleville washer 2130, ahermetic seal is formed between the axial hole, the first insulatingwasher 2124, the second insulating washer 2126, and the secondstud/collector disk/terminal post 2120.

Similarly, the welding of the lid 2118 to the lip of the can 2122, andthe welding of the lid 2118 to the first terminal post 2116 form anotherhermetic seal.

The hole 2146 in the lid 2118 remains and serves as a fill port for anelectrolyte solution, which may be made up of a solvent in the salt, asdescribed above. Once the electrolyte solution is in the can (i.e.,drawn into the can under vacuum, as described above), a bushing 2148 isthen placed into the hole 2146, and is seated against a flange 2150 atan interior edge of the hole 2146. The bushing 2148 is a hollow cylinderin shape, fashioned to receive a plug 2152.

The plug 2152, which is cylindrical in shape, is next pressed into acenter of the bushing 2148, thereby compressing the bushing 2148 againstan interior of the hole 2146 and forming a hermetic seal between thehole 2146, the bushing 2148, and the plug 2152.

The plug 2152 and the bushing 2148 may be selected to dislodge when aprescribed level of pressure is reached within the electrochemicaldouble layer capacitor, thereby forming an overpressure safetymechanism.

FIG. 22 is a top view of a second stud/collector disk/terminal post 2120of the second terminal assembly 2104 of the variation of FIG. 21.

Shown are a collector disk portion 2142, and a terminal post portion2144. A stud portion 2140 (FIG. 21) is also shown. The terminal postportion 2144 includes a threaded portion for engaging the locknut 2132(FIG. 21), and thereby allowing the locknut 2132 (FIG. 21) to betightened down onto the terminal post portion 2144 during assembly asdescribed above.

Advantageously by forming the stud portion 2140 (FIG. 21), the collectordisk portion 2142, and the terminal post portion 2144 in a single unit,the assembly steps and the number of pieces required to construct theelectrochemical double layer capacitor of the present embodiment arereduced, thereby reducing cost and complexity.

FIG. 23 is a top view of a stud/collector disk/terminal post 2120 of thesecond terminal assembly 2104 of the variation of FIG. 21.

Shown are a stud portion 2140, a collector disk portion 2142, and aterminal post portion 2144. The terminal post portion 2144 includes athreaded portion for engaging the locknut 2132 (FIG. 21), and therebyallowing the locknut 2132 (FIG. 21) to be tightened down onto theterminal post portion 2144 during assembly as described above.

FIG. 24 is a side view of a stud/collector disk 2400 of the secondterminal of the variation of FIG. 21.

Shown are a stud portion 2402, a collector disk portion 2404, and athreaded portion 2406. The threaded portion 2404 is inserted into athreaded hole in the second terminal post (not shown) during assembly,as described above.

FIG. 25 is a top view of a stud/collector disk 2400 of the firstterminal of the variation of FIG. 21.

Shown are the collector disk portion 2404 and the threaded portion 2406along with a notched cylindrical portion 2502. The notched cylindricalportion 2502 is used to apply a rotational force to the threaded portion2406 as the threaded portion is assembled with the second terminal post(not shown), such as by using a tool that engages flat surfaces ofnotches in the notched cylindrical portion 2502. The notches in thenotched cylindrical portion 2502 do not affect the surface area of thecollector disk that contacts the second electrode at the second end ofthe “jellyroll.”

Referring to FIG. 26, a side cross-sectional view is shown of anothervariation of the “jellyroll” embodiment of FIGS. 12 through 20,employing a pocket 2602 in the can in a modified second electrodeassembly.

Shown are the “jellyroll” electrode assembly 1200 of FIG. 13, a firstcollector disk 1404, a first terminal post 1504, a lid 1506, a firstinsulating washer 1702, a second insulating washer 1802, a flat washer1804, a Belleville washer 1806, a locknut 1808, a hole 1902 in the lid1506, a second collector disk 1604, second terminal post 1504, a can1704, and the pocket 2602 in the can 1704.

The “jellyroll” electrode assembly 1200 is prepared in accordance withthe process described above, and the first and second collector disks1404, 1604, and the first and second terminal posts 1504, 1606 areaffixed to the “jellyroll” electrode assembly 1200, such as by laserwelding or arc spraying, as described above. Next, the “jellyroll”electrode assembly 1200, with the respective first and second collectordisks 1404, 1604, and first and second terminal posts 1504, 1606, isslid into the can 1704 (with the second terminal post 1606 entering thecan 1704 first). The second terminal post 1606 seats in an interior ofthe pocket 2602 in the can 1704 as the “jellyroll” electrode assembly1200 is slid into the can 1704, and the pocket 2602 is crimped againstthe second terminal post 1606, so as to electrically and mechanicallyconnect the second terminal post 1606 to the interior of the pocket2602. An exterior of the pocket serves as a first terminal of theelectrochemical double layer capacitor 1200.

Next, the first insulating washer 1702 is slid over the first terminalpost 1504, and then the lid 1506 is inserted into the can 1704 over thefirst terminal post 1506. A rim of the lid 1506 is welded to a lip ofthe can 1704, as described above, so as to form a hermetic seal. Thesecond insulating washer 1802, the flat washer 1804, and the Bellevillewasher 1806 are slid over the first terminal post 1504, and the locknut1808 is tightened down onto the Belleville washer 1806, so as to form afurther hermetic seal.

The electrolyte solution is then introduced into the can through thehole 1902 in the lid, as described above, and the bushing (not shown),and plug (not shown) are used to form a hermetic seal at the hole 1902in the lid.

Referring to FIG. 27, a side cross-sectional view is shown of anothervariation of the “jellyroll” embodiment of FIGS. 12 through 20,employing a crimp seal to secure a crimp lid 2702 to the can 1704, andemploying a pocket 2704 in the lid 2702 in a modified first electrodeassembly.

Shown are the “jellyroll” electrode assembly 1200 of FIG. 13, a firstcollector disk 1404, a first terminal post 1504, a crimp lid 2702, asecond collector disk 1604, a second terminal post 1606, a can 1704, anda pocket 2602 in the can 1704, and a pocket 2704 in the crimp lid 2702.

The “jellyroll” electrode assembly 1200 in prepared in accordance withthe process described above, and the first and second collector disks1404, 1604, and the first and second terminal posts 1504, 1606 areaffixed to the “jellyroll” electrode assembly 1200, such as by laserwelding or arc spraying, as described above. Next, the “jellyroll”electrode assembly 1200, with the respective first and second collectordisks 1404, 1604, and first and second terminal posts 1504, 1606, isslid into the can 1704 (with the second terminal post 1606 entering thecan 1704 first). The second terminal post 1606 seats in an interior ofthe pocket 2602 in the can 1704 as the “jellyroll” electrode assembly1200 is slid into the can 1704, and the pocket 2602 in the can 1704 iscrimped against the second terminal post 1606, so as to electrically andmechanically connect the second terminal post 1606 to the interior ofthe pocket 2602. An exterior of the pocket serves as a second terminalof the electrochemical double layer capacitor.

Next, the electrolyte solution is introduced into the can, as describedabove.

Then, a seal 2706 is placed onto a lip of the can 1704, and the crimplid 2702 is placed into the opening of the can 1704, with a rim of thecrimp lid 2702 engaging the seal 2706. The first terminal post 1504seats in an interior of the pocket 2704 in the crimp lid 2702 as thecrimp lid 2702 is placed into the opening of the can 1704.

The lip of the can 1704 is crimped onto the rim of the crimp lid 2704,with the seal 2706 being interposed thereinbetween, so as to form ahermetic seal between the crimp lid 2704 and the can 1704.

An interior of the pocket 2704 in the crimp lid 2702 is then crimpedagainst the first terminal post 1504, so as to electrically andmechanically connect the first terminal post 1504 to the pocket 2704 inthe crimp lid 2702. An exterior of the pocket 2704 in the crimp lid 2702serves as a first terminal of the electrochemical double layercapacitor.

Referring to FIG. 28, a side cross-sectional view is shown of anothervariation of the “jellyroll” embodiment of FIGS. 12 through 20,employing a low profile “can-within-a-can” assembly and modified firstand second electrode assemblies.

Shown are the “jellyroll” electrode assembly 1200 of FIG. 13, a firstcollector disk 1404, a first terminal post 1504, a second collector disk1604, a second terminal post 1606, an inner can 2802, an outer can 2804,a pocket 2806 in the inner can 2802, and a pocket 2808 in the outer can2804.

The “jellyroll” electrode assembly 1200 is prepared in accordance withthe process described above, and the first and second collector disks1404, 1604, and the first and second terminal posts 1504, 1606 areaffixed to the “jellyroll” electrode assembly 1200, such as by laserwelding or arc spraying, as described above.

A seal 2810 is then placed at a periphery of an interior basal end ofthe outer can 2804.

Next, the “jellyroll” electrode assembly 1200, with the respective firstand second collector disks 1404. 1604, and first and second terminalposts 1504, 1606, is slid into the outer can 2804 (with the secondterminal post 1606 entering the outer can 2804 first). The secondterminal post 1606 seats in an interior of the pocket 2808 in the outercan 2804 as the “jellyroll” electrode assembly 1200 is slid into theouter can 2804, and the pocket 2808 is crimped against the secondterminal post 1606, so as to electrically and mechanically connect thesecond terminal post 1606 to the pocket 2808 in the outer can 2804. Anexterior of the pocket serves as a second terminal of theelectrochemical double layer capacitor.

The inner can 2802 is then slid into the outer can 2804, with a lip ofthe inner can 2802 engaging the seal 2810 at the periphery of theinterior basal end of the outer can 2804. As the inner can 2802 is slidinto the outer can 2804, an interior of the pocket 2806 in the inner can2802 engages the first terminal post 1404.

A lip of the outer can 2804 is then crimped against a periphery of anexterior basal end of the inner can 2802, so as to form a hermetic sealat the periphery of the interior basal end of the outer can 2804, andthe lip of the inner can 2802, with the seal 2810.

The pocket 2806 in the inner can 2802 is then crimped against the firstterminal post 1404, so as to electrically and mechanically connect thefirst terminal post 1404 to the pocket 2806 in the inner can 2802. Anexterior of the pocket 2806 in the inner can 2802 serves as a firstterminal of the electrochemical double layer capacitor.

The electrolyte solution is then introduced into the inner and outercans 2802, 2804 through a hole 2812 in the end of the outer can 2804,and a bushing (not shown), and plug (not shown) are used to form ahermetic seal at the hole 1812 in the outer can 1804, as describedabove.

Referring to FIG. 29, a side cross-sectional view is shown of anothervariation of the “jellyroll” embodiment of FIGS. 12 through 20,employing a ceramic seal 2902 between the lid 2904 and the firstterminal assembly.

Shown are the “jellyroll” electrode assembly 1200 of FIG. 13, a firstcollector disk 1404, a first terminal post 1604, a lid 2904, a ceramicseal 2902, a second collector disk 1604, second terminal post 1606, acan 1704, and a pocket 2602 in the can 1704.

The “jellyroll” electrode assembly 1200 is prepared in accordance withthe process described above.

Next, the ceramic seal 2902 is bonded to the first terminal post 1504,and the lid 2904 is bonded to the ceramic seal 2902, such as bydiffusion bonding, so as to form a hermetic, insulating seal between theceramic seal 2902 and the first terminal post 1404, and between theceramic seal 2902 and the lid 2904.

Then, the first and second collector disks 1404, 1604, and the first andsecond terminal posts 1504, 1606 are affixed to the “jellyroll”electrode assembly 1200, such as by laser welding or arc spraying, asdescribed above.

Next, the “jellyroll” electrode assembly 1200, with the respective firstand second collector disks 1404, 1604, and first and second terminalposts 1504, 1606, is slid into the can 1704 (with the second terminalpost 1504 entering the can 1704 first). The second terminal post 1604seats in an interior of the pocket 2602 in the can 1704 as the“jellyroll” electrode assembly 1200 is slid into the can 1704, and thepocket is crimped against the second terminal post 1504, so as toelectrically and mechanically connect the second terminal post 1604 tothe pocket 2602. An exterior of the pocket serves as a second terminalof the electrochemical double layer capacitor.

A rim of the lid 2904 is welded to a lip of the can 1704, as describedabove, so as to form a hermetic seal.

The electrolyte solution is then introduced into the can 1704 through ahole (not shown) in the lid 2904, and a bushing (not shown), and plug(not shown) are used to form a hermetic seal at the hole (not shown) inthe can 1704, as described above.

While the invention herein disclosed has been described by the specificembodiments and applications thereof, numerous modifications andvariations could be made thereto by those skilled in the art withoutdeparting from the scope of the invention set forth in the claims.

1. A method of making an electrode structure for use in a double layercapacitor, comprising the steps of: forming a plurality of electrodes,each of the plurality of electrodes comprising: a current collectorplate; a primary coating formed on a portion of each side of the currentcollector plate as a slurry, the primary coating including conductingcarbon powder and a binder; and a secondary coating formed on eachprimary coating as a slurry, the secondary coating including activatedcarbon powder, a solvent and a binder; positioning a respectiveseparator between two adjacent electrodes of the plurality of electrodeswhile stacking the plurality of electrodes on top of each other suchthat the respective separator is juxtaposed against respective secondarycoatings of adjacent ones of the plurality of electrodes, wherein therespective separator electrically insulates the adjacent ones of theplurality of electrodes from each other, whereby forming a stack of theplurality of electrodes with a respective separator positioned inbetween respective ones of the plurality of electrodes; and rolling theelectrode stack starting at one end of the electrode stack into acylindrical structure.
 2. The method of claim 1 further comprisingelectrically coupling together a first set of respective ones of aportion of each current collector plate that do not have the respectiveprimary coating formed thereon to form a first terminal.
 3. The methodof claim 2 further comprising electrically coupling together a secondset of respective ones of the portion of each current collector platethat do not have the respective primary coating formed thereon to form asecond terminal.
 4. The method of claim 3 further comprising insertingthe rolled electrode stack into a capacitor can; coupling the firstterminal to a first capacitor terminal of the capacitor can; couplingthe second terminal to a second capacitor terminal of the capacitor can;saturating the rolled electrode stack in a prescribed electrolyticsolution; and; sealing the rolled electrode stack and the prescribedelectrolytic solution within the capacitor can.
 5. The method of claim 1wherein the positioning while stacking steps are performed such thatupon rolling the electrode stack, a portion of each current collectorplate that does not have a respective primary coating formed thereonextends from a respective end of the rolled electrode stack.
 6. Themethod of claim 5 wherein the positioning while stacking steps areperformed such that upon rolling the electrode stack, the portion ofeach current collector plate that does not have the respective primarycoating formed thereon extends from an opposite end of the rolledelectrode stack as extends the portion of each adjacent currentcollector in the electrode stack that does not have the respectiveprimary coating formed thereon.
 7. The method of claim 6 furthercomprising smearing together portions of the current collector platesextending from each end of the electrode stack into electrical contactwith each other.
 8. The method of claim 7 further comprising applying aconductive coating to a portion of the current collector plates smearedtogether at each end of the electrode stack, each conductive coatingadapted to be coupled to a respective capacitor terminal.
 9. A method ofmaking an electrode structure for use in a double layer capacitor,comprising the steps of: providing a current collector plate having alength and a width and a thickness; providing a primary coating formedon a portion of each side of the current collector plate as a slurry,the portion covering an area extending the full length of the currentcollector plate and extending a portion of the width of the currentcollector plate, the primary coating including conducting carbon powderand a binder; and a secondary coating formed on each primary coating asa slurry, the secondary coating including activated carbon powder, asolvent and a binder; positioning a respective separator between twoadjacent electrodes of the plurality of electrodes while stacking theplurality of electrodes on top of each other such that the respectiveseparator is juxtaposed against respective secondary coatings ofadjacent ones of the plurality of electrodes, wherein the respectiveseparator electrically insulates the adjacent ones of the plurality ofelectrodes from each other, whereby forming a stack of the plurality ofelectrodes with a respective separator positioned in between respectiveones of plurality of electrodes, the electrode stack having a stacklength and a stack width; and rolling the electrode stack starting, atone end of the electrode stack along the stack length into a cylindricalstructure.
 10. The method of claim 9 further comprising electricallycoupling together a first set of respective ones of the portion of eachcurrent collector plate that do not have the respective primary coatingformed thereon to form a first terminal.
 11. The method of claim 10further comprising electrically coupling together a second set ofrespective ones of the portion of each of the plurality of electrodesthat do not have the respective primary coating formed thereon to form asecond terminal.
 12. The method of claim 9 wherein the positioning whilestacking steps are performed such that upon rolling the electrode stack,a portion of each current collector plate that does not have arespective primary coating formed thereon extends from a respective endof the rolled electrode stack.